Proximity fuse for missiles

ABSTRACT

A compact fuse designed to be armed after cessation of acceleration and provided with a plurality of safety means; a cap adapted to be set in an inoperative position by a rotation of 90* with reference to the fuse body, a cover for the cap adapted to collapse towards the striker and to prevent its releasing operation in case of a premature impact, a detonator-carrier adapted to be shifted laterally out of registry with the striker, a weight controlled by inertia and controlling operation of the striker and an arming weight releasing through inertia in striker.

United States Patent [1 1 Nathan et a1.

[ 1 Oct. 8, 1974 PROXIMITY FUSE FOR MISSILES [75] Inventors: Guy E.Nathan,

' lssy-Les-Moulineaux; Claude A.

Varaud, Nogent-Sur-Mar, both of France [73] Assignee: ConstructionsNavales et lndustrielles de la Mediterranee C.N.I.M., Paris, France 22Filed: Apr. 9, 1973 21 Appl. No.: 349,124

[30] Foreign Application Priority Data Apr. 10, 1972 France "72.12527[52] U.S.'Cl. 102/702 P, 102/76 R, 102/78 [51] Int. Cl F420 15/00, F42C13/00 [58] Field 01' Search 102/702 R, 70.2 P, 78,

102/76 P, 76 R; 343/7 PF [56] References Cited I UNITED STATES PATENTS1/1959 Saloranta et al 102/78 2,900.911 8/1959 Stath'am 102/702 P2,951,444 9/1960 Hunt, Jr. et a1 102/78 3,151,558 10/1964 Lunati 102/78Primary Examiner-Benjamin A. Borchelt Assistant Examiner- C. T. JordanAttorney, Agent, or Firm-Finnegan, Henderson, Farabow & Garrett [5 7]ABSTRACT A compact fuse designed to be armed after cessation ofacceleration and provided with a plurality of safety means; a capadapted to be set in an inoperative position by a rotation of 90 withreference to the fuse body, a cover for the cap adapted to collapsetowards the striker and to prevent its releasing operation in case of apremature impact, a detonator-carrier adapted to be shifted laterallyout of registry with the striker, a weight controlled by inertia andcontrolling operation of the striker and an arming weight releasingthrough inertia in striker.

3 v Claims, Drawing Figures um 8l974 PAIENTEU sum 10F 3 839 963PROXIMITY FUSE FOR MISSILES The present invention has for its objectpreventing premature ignition of a fuse and ensuring fuse ignition upona missile reachinga point at a predetermined distance from the objectiveor from grounder upon impact therewith. Fuses of this type are alreadyknown which are generally extremely complex both electrically andmechanically and which are not wholly reliable for all conditions ofuse.

The invention removes these drawbacks by means of a fuse for missiles,of the type considered, which is mechanically and electrically verysimple while it is perfectly reliable.

Briefly described, the invention comprises a fuse including a caprotatable with reference to the fuse body and terminating with a conicalpoint forming a deformable radome, the deformable radome protecting thedetecting aerial and being rigid with the electronic system forming acompact unit which is slidable after the manner of a striker piston. Thefuse also employs a mechanism including a detonator-carrier adapted toslide transversely within the body under the action of a spring or ofcentrifugal force, if required, said detonator-carrier being heldnormally aside by the end of the rod of an axial striker the front endof which forms a cylindrical tailpiece round which is slidingly fitted astriker weight urged forwardly by a spring and locked in its inoperativeposition by a first ball engaging a first groove in the tail-piece. Saidfirst ball is itself held in position by a second ball or the like partadapted to move transversely and locked by an arming weight adapted tomove within the cap in parallelism with the striker and to be urgedforwardly by a further spring while it includes an extension towards therear constituted by a rod passing through the spring.

The striker weight includes further locking means constituted, forinstance, by a circlips adapted to be locked within a further groove ofthe tail-piece after the said weight has traveled sufficiently'towardsthe rear upon starting of the missile and after the arming weight hasitself receded through inertia and has thus released the balls. When thestriker weight is returned forwardly under the action of its spring, thefront end of the striker tail-piece engages the striker piston and,simultaneously, its rear tip releases the detonator-carrier permittingits transverse movement which sets the detonator in front of said tipand closes at the end of its travel the general switch controlling theelectronic circuitry.

The mechanism includes furthermore an electric primer arranged inparallelism within the striker and communicating through ports formedwithin the cap and the body with the main detonator when the latter ismoved into an axial position. The electric primer is connected with theelectronic detecting means through a delaying condenser. The wholearrangement is such that after a rotation, through say 90, of the capwith reference to the fuse body, the port connecting the electric primerin the cap registers no longer with the corresponding port inthe fusebody whereby the first series of firing means. is severed while the rearrod on the arming weight registers no longer with its releasing port inthe body, which severs the second series of firing means by locking thestriker in its rearmost position, this forming a second safetypreventing the transverse movement of the detonator-carrier and cuttingoff the double pyrotechnical chain together with the electric circuit.

An embodiment of the invention will now be described by way of exampleand by no means in a limiting sense. Said embodiment is illustrated inthe accompanying drawings wherein.

FIG. 1 is an axial cross-sectional view of a missile proximity fuseformed in accordance with this invention.

FIG. 2 is an axial cross-section, at right angles with that of FIG. 1,through line IIII of FIG. 4.

FIG. 3 shows on a larger scale a detail of the central portion of FIG.1.

FIG. 4 is a transverse cross-section through line IV-IV of FIG. 1.

FIG. 5 is a cross-section through line V-V of FIG. 1.

DETAILED DESCRIPTION The fuse illustrated includes a body 1 and a cap 2revolvably carried by said body 1 over which it is held by an expansiblering 3 held by a screw 4 (FIG. 2) both inside a groove in the cap and agroove in the extension 5 of the body inside the cap.

The body 1 includes a rear threaded section 6 so that it may be screwedas usual into the nose of a missile. The cap 2 is provided with a'cover7 of a plastic perme able for hyperfrequency waves and acting as aradome while being sufficiently deformable. Inside said cover 7 ishoused the aerial 8 of the hyperfrequency system forming a proximityradar system.

According to the invention, the system including the aerial 8, thehyperfrequency circuit 9 and the electronic detecting circuit 10 iscarried as a compact unit within a metal socket 11 by means of a moldedpiece of plastic, the whole arrangement being fitted inside a borelocated to the front of the cap 2, so as to slide axially. Thereby, inthe case of a failure of the electromagnetic detecting means, the fusewill operate under direct impact against the target, the deformation ofthe cover 7 allowing said sliding arrangement to operate as a strikerpiston while it is urged forwards when inoperative by a spring 12a.

The actual mechanical part of the fuse includes a central metal block 13bored axially at 14, a tubular striker weight 15 slidably mounted insaid bore 14 and being permanently urged forwardly by a spring 16.Inside the bore in the striker weight may slide in its turn, thecylindrical tailpiece 17 of a striker 18, ending to the rear with apointed end and slidingly engaging the center of a disc 20 rigid withthe block 13 rigidly secured in its turn to the cap 2 by means of ascrew 21 (FIGS. 1 and 4).

The same block-13 is provided with a further bore 22 parallel with thecentral bore 14 (FIG. 1) and wherein an arming weight 23 slides, whicharming weight is urged forwardly by a spring 24. The arming weight 23extends rearwardly, so as to form the rear tail-piece 25 of a smallerdiameter passing through the spring 24 and slidingly engaging a port 26in the disc 20.

In its inoperative position, as clearly shown in FIG. 3, the weight 23locks a ball 27 housed inside a transverse bore 28 in the block 13 andacting on a further ball 29 housed in a bore 30 in the weight 15associated with the striker, said ball 29 engaging anannular groove 31in the tail-piece 17 of the striker. Now, the weight 15 on the strikeris provided with a milled portion 30a which allows the ball 27 to enterslightly within said weight, so as to prevent its rotation. Thetransverse bore 28 opens into the longitudinal bore 22 through apreferably hammered or crimped clearance port as shown in FIG. 3, so asto prevent the ball 27 dropping into said bore 22.

The tail-end 17 of the striker is provided with a further sharp-edgedannular groove 32 adapted to cooperate with a circlips 32a engaging agroove and slot in the weight of the striker, so as to ensure theinterlocking of the parts 15 and 17. At the upper end of the block 13there is inserted a further disc 33 against which the arming weight 23normally abuts.

Within the body 1 there is fitted another metal block 34 in which thereis milled a parallelepipedic housing 35 the rear opening of which isclosed by a disc 36 while a transversely shiftable substantiallyparallelepipedic detonator-carrier 37 is slidingly carried inside saidhousing. A bore provided in said detonator-carrier is engaged by thedetonator 38 the front end of which registers with a port 39 in thecarrier 37 while a further smaller bore 40 in said carrier inparallelism with the first-mentioned bore is adapted to house the reartip 19 of the striker when the detonator-carrier 37 is in its outermostposition illustrated in FIGS. 1 and 2. A return spring 41 housed in thethreaded plug 42 urges normally the detonator-carrier 37 in thedirection of the arrow 43 (FIG. 2) if the fuse is intended forcooperation with a self-propelled or semi-self-propelled missile. On thecontrary, if the fuse is to be fitted on a missile fired by a rifledbore, the return spring may be replaced by an eccentric weight thecentrifugal force acting on which urges the detonator-carrier in thedirection of said arrow 43.

As is shown in FIG. 1, the block 34 and also the body 1 are providedwith a longitudinal bore 44 affording a passage towards the rear for therear tail-piece 25 of the arming weight 23.

In alignment with the axis of the striker 18, that is axially of thefuse body, a port 45 extends through the disc 36. To the rear of saidport 45, there is a tube 46 filled with an explosive acting as a relayfor the explosive in the detonator 38 when the latter faces the striker,said relay acting then on the booster charge 47 enclosed in thecup-shaped member 48 screwed over the rear end of the body 1.

The central block 13 is laterally milled at 49 (FIGS. 2 and 4), so as tohouse a block 50 of plastic in which are embedded a number of electricparts including an electric primer 51 with its feeding wires. The flameproduced by said primer 51 is transmitted through the sloping bore 52inthe disc and a further sloping bore 53 in the auxiliary block 34, to thedetonator 38 through the port 39 when the latter registers with the fuseaxis as described below. Inside said block 50 is also embedded acondenser 54 feeding the electric primer 51 into which it is dischargedupon detection by the circuit l0.

Lastly, the rear extension 55 of the plastic block 50 passes through thefuse body as provided by suitable openings, which allows the cap 2 toturn by one quarter of revolution with reference to the body 1, saidextension 55 serving thus as an abutment for such a rotation. The rearend of the extension 55 carries two connectors 56 adapted to engagecorresponding parts in a further block of plastic 57 in which areembedded the supply batteries 58, said block 57 being revolvable aroundthe explosive-filled tube 46. The extension 55 of the block 50 isprovided furthermore with a transverse port 59 inside which lie twoelastic conductive blades 60 adapted to be short-circuited uponinsertion between them of a shaped member 61 having an annular retaininggroove. The shaped member 61 is fitted in the detonator-carrier 37 withthe interposition of an insulating sleeve 62.

The two conductive blades are inserted in a circuit section passingthrough one of the connectors while the other connector ensures directfeeding. Of course, in order to ensure operation, it is essential toelectrically connect the parts embedded or carried in the plastic block12 with those carried by the plastic block 50 and its extension 55. Thiscan be obtained by yielding wires which are not illustrated without thisleading to any difficulty since the two blocks 12 and 50 do not revolvewith reference to each other and, furthermore, move towards each otheronly upon impact, that is at a moment when the electric connections areno longer necessary. In contradistinction, the electric connectionsbetween the blocks 55 and 57 are rigid by reason of the above'disclosedpossibility of rotation of the block 57, so as to avoid the drawbacksarising from the use of a connection through yielding wires.

In order to make the operation more readily understandable, it will befirst assumed that the fuse is adjustable for operation as illustrated,that is the cap 2 is angularly set on the body 1 in a manner such thatthe oblique bores 52 and 53 register and that the port 26 registers alsowith the bore 44.

Upon starting of the missile, the acceleration to which the fuse issubjected produces through inertia the recoil of the arming weight 23which, after a sufficient travel, releases the ball 27 which, in itsturn, releases the ball 29. This allows the striker weight 15 to recedealso through inertia within the bore 14 and, provided theacceleration'is sufficiently lasting, to reach a position for which itscirclips 32a drops into the groove 32 of the tail-piece 17 of thestriker. When the acceleration ceases, the striker weight 15 returnsforwardly under the action of the spring 16 and carries along with itthe actual striker 18. This produces two results: on the one hand, thefront end of the striker tail-piece 17 engages the block 12 and, on theother hand, the rear end 19 of the striker passes completely out of thebore 40 and releases the detonator-carrier 37. The latter moves underthe action of the spring 41, or possibly of centrifugal force, in thedirection of the arrow 43 and this leads, on the one hand, to make theport 39 and the detonator 38 register with the axis of the fuse and thusface the striker tip and, on the other hand, to set the shaped member 61between the connecting blades 60, which closes the circuit feeding theelectronic system.

The battery 58 feeds then the circuit of the radar and of the detectorand loads the condenser 54 which, after a delay of say 5 to 6 seconds,is ready to operate. The missile continues its flight until the radardetects the presence of a target or the proximity of ground. At such amoment, and for a predetermined distance, the electronic system causesthe discharge of the condenser 54 into the primer 51, which leads to thefiring of the detonator 38 and consequently to the explosion of themissile. This corresponds to normal operation.

In case of a failure ascribable to misoperation of one of the sequentialparts, the exploding of the missile is nevertheless ensured upon impactof the latter against a target or against ground. In fact, in such acase, the cover 7 is crushed and the piston-shaped block 12 pushes thetail-piece 17 of the striker which hits directly on the detonator 38.

When handling the missile, before the starting of the shot, but afterthe cap has been set in its operative position, safety is howeverensured through the fact that if the missile is dropped for instance,the acceleration to which the fuse is subjected is not sufficient, as tointensity and as to duration, for producing in succession the completecollapse of the arming weight 23. This is true even if the missile fallsupon its tip since the striker in its rearmost position cannot moveforwards and furthermore neither the detonator 38 nor the electricprimer 51 can initiate the explosion. Still more, thearming weight 23 isbraked by the thrust exerted by the balls in proportion with theviolence of the shock, the outline of the groove 31 having a largerradius than the ball 29.

On the other hand, upon firing of the missile, the safety at the muzzleis ensured by the fact that throughout the duration of the accelerationand even after collapse of the arming weight 23 and after the strikerweight 15 has receded, the spring 16 remains compressed, so that saidstriker weight 15 cannot bring the tail-piece 17 into contact with theelectronic block 12. If the missile meets an obstacle during itsacceleration, the block 12 is pushed inwardly and the tail-piece 17 ofthe striker can no longer travel far enough for releas ing thedetonator-carrier 37 when the acceleration has come to end, which asprecedingly breaks both the electric circuit and the two 'pyrotechnicalsequential parts. If, on the'contrary, no hindrance is .then met by themissile and, after the fuse has been completely armed, the radar detectsimmediately beyond the muzzle the proximity of an obstacle, the missilecannot yet explode since the electric circuit has not been closed forenough time for loading the condenser 54. It has been stated that thetime required for such a loading is of'a magnitude of 5 to 6 seconds andthis allows the missile to be several miles beyond the muzzle before itcan operate.

Of course, during transportation and dropping with a parachute, the cap2 must be turned round its axis through say 90 with reference to thebody 1, so as to be set in a safety position. Under such conditions andin addition to all the above described safeties, said rotation causesthe rear tail-piece 25 of the arming weight and the bore 26 in the discto be out of registry with the bore' 44 in the block 34, whichpositively locks the mechanical part of the fuse and the correspondingsafety means. Simultaneously, the sloping bores 52 and 53 are out ofregistry, which produces a gap in the pyrotechnical chain of sequentialparts adjacent the electric primer 51 while the electric circuit isbroken by the locking of the detonator carrier in its inoperativeposition, the port 39 and the detonator 38 being also out of registrywith the bore 53 and the tube 46.

Absolute safety is thus obtained through a plurality of means, so thatnothing whatever can lead to an explosion during transportation ordropping through a parachute. The fuse according to the invention hasthus reached a high degree of reliability and safety while it iscomparatively simple, sturdy and of a reduced bulk.

Obviously many modifications may be brought to the above describedembodiment and certain parts may be replaced by equivalent parts withoutwidening thereby the scope of the invention as defined by theaccompanying claims.

What we claim is:

l. A proximity fuse for missiles, including a body adapted to be fittedon the nose of a missile and a cap revolvably carried by the body andprovided with a cover forming a radome permeable to hyperfrequencyradiation, said fuse being characterized by the fact that the radome isinade of a deformable material and encloses a detecting aerial rigidlymounted on an electronic section adapted to slide inside the cap so asto form a striking plunger, said section including detecting means, thefuse including a detonator-carrier and detonator adapted to slidetransversely in the body, first means for applying a transverse force onsaid detonator-carrier, switch means responsive to saiddetonatorcarrier, said detonator-carrier being normally held in aninoperative position by the rear tip of the rod of an axial strikerhaving a fronttail-piece, a striker weight slidable on said tail-pieceand urged forwardly by a spring and locked when inoperative by a firstball engaging an annular groove in said tail-piece, said first ballbeing held in said annular groove by second means adapted to movetransversely and locked in its normal position by an arming weightadapted to move' inside the cap along a line parallel with the strikerweight and urged forwardly by a further spring, said arming weightincluding a rearward extension passing through said further spring andaligned with a port when the cap and body are in a first position, thirdmeans on the striker weight adapted to engage a further groove in thestriker tail-piece after the striker weight has traveled a predetermineddistance in a rearward direction upon firing of the missile and afterthe arming weight has itself been shifted rearwardly through inertia andhas thus released the first ball and second means, the striker weighthaving first returned forwardly under the action of its spring, thefront end of the striker tail-piece engages the'striking plunger whilethe striker rear tip releases the detonator-carrier for transversemovement to bring the detonator into its operative position in front ofsaid rear tip and to close at the end of its stroke said switch means,said swtich means controlling an electronic circuit including a battery,an electric primer arranged in parallel with the striker communicatingthrough channels formed in the cap and in the body with said detonatorwhen said detonator is brought into its operative position, said primerbeing connected with the detecting means through a delaying condenser,rotation of the cap'with reference to the fuse body to a second positioncauses the channel in the cap connected with the electric primer to beout of registry with the corresponding channel in the fuse body toprevent fuse ignition while the rear tail-piece on the arming weight isout of registry with said port provided in the fuse body to furtherprevent fuse ignition by preventing transverse movement of thedetonator-carrier.

2. A fuse as claimed in claim 1, wherein the switch means includes twoelastic conductive blades having an interval therebetween, a conductivemember provided with an annular retaining groove mounted on thedetonator-carrier in alignment with said interval whereby transversemovement of said detonatorthe cap with reference to the body, therearward extension of the first block ending with connecting plugsengaging a second block of plastic molded over the battery, a rearbooster and a tube containing an explosive forming a pyrotechnic relaybetween the detonator and the rear booster, the second block surroundingsaid tube and mounted for rotation thereabout.

1. A proximity fuse for missiles, including a body adapted to be fittedon the nose of a missile and a cap revolvably carried by the body andprovided with a cover forming a radome permeable to hyperfrequencyradiation, said fuse being characterized by the fact that the radome ismade of a deformable material and encloses a detecting aerial rigidlymounted on an electronic section adapted to slide inside the cap so asto form a striking plunger, said section including detecting means, thefuse including a detonator-carrier and detonator adapted to slidetransversely in the body, first means for applying a transverse force onsaid detonator-carrier, switch means responsive to saiddetonator-carrier, said detonator-carrier being normally held in aninoperative position by the rear tip of the rod of an axial strikerhaving a front tail-piece, a striker weight slidable on said tail-pieceand urged forwardly by a spring and locked when inoperative by a firstball engaging an annular groove in said tail-piece, said first ballbeing held in said annular groove by second means adapted to movetransversely and locked in its normal position by an arming weightadapted to move inside the cap along a line parallel with the strikerweight and urged forwardly by a further spring, said arming weightincluding a rearward extension passing through said further spring andaligned with a port when the cap and body are in a first position, thirdmeans on the striker weight adapted to engage a further groove in thestriker tail-piece after the striker weight has traveled a predetermineddistance in a rearward direction upon firing of the missile and afterthe arming weight has itself been shifted rearwardly through inertia andhas thus released the first ball and second means, the striker weighthaving first returned forwardly under the action of its spring, thefront end of the striker tail-piece engages the striking plunger whilethe striker rear tip releases the detonator-carrier for transversemovement to bring the detonator into its operative position in front ofsaid rear tip and to close at the end of its stroke said switch means,said swtich means controlling an electronic circuit including a battery,an electric primer arranged in parallel with the striker communicatingthrough channels formed in the cap and in the body with said detonatorwhen said detonator is brought into its operative position, said primerbeing connected with the detecting means through a delaying condenser,rotation of the cap with reference to the fuse body to a second positioncauses the channel in the cap connected with the electric primer to beout of registry with the corresponding channel in the fuse body toprevent fuse ignition while the rear tail-piece on the arming weight isout of registry with said port provided in the fuse body to furtherprevent fuse ignition by preventing transverse movement of thedetonator-carrier.
 2. A fuse as claimed in claim 1, wherein the switchmeans includes two elastic conductive blades having an intervaltherebetween, a conductive member provided with an annular retaininggroove mounted on the detonator-carrier in alignment with said intervalwhereby transverse movement of said detonator-carrier effects insertionof said conductive member into said interval to complete an electricalcircuit.
 3. A fuse as claimed in claim 1, wherein the cap carries afirst block of plastic molded over the switch means controlling theelectric circuit, the condenser, the electric primer and theirconnections, said first block extending rearwardly through an opening inthe fuse body which provides abutments for the rotation of the cap withreference to the body, the rearward extension of the first block endingwith connecting plugs engaging a second block of plastic molded over thebattery, a rear booster and a tube containing an explosive forming apyrotechnic relay between the detonator and the rear booster, the secondblock surrounding said tube and mounted for rotation thereabout.